U.S. Pat. No. 4,663,725, which is assigned to the same assignee as the present application, discloses the use of microprocessor based transport refrigeration control for use with a refrigerated container, with the refrigerant compressor being driven by an electric motor. The use of a microprocessor is used to operate the various components of a refrigeration unit according to predetermined algorithms, and to detect and record faults which occur during the operation thereof.
U.S. Pat. No. 4,918,932, which is assigned to the same assignee as the present application, discloses the use of a microprocessor in the control of a transport refrigeration unit to determine average error between an operator selected set point temperature and the temperature of a space to be conditioned, using the outputs of return air and discharge air sensors, and the use of the average error in the determination of an error signal which modulates the capacity of the transport refrigeration unit.
While these patents ably utilize the capabilities of a microprocessor during the operation of a transport refrigeration unit, it would be desirable, and it is an object of the present invention, to further utilize the capabilities of the microprocessor which operates the unit, for directing a completely automatic, comprehensive pre-trip diagnostic procedure which detects malfunctions and marginal operation of the unit before it leaves a terminal with a new load. Such a pre-trip diagnostic procedure would also be available as an aid in the testing of the unit at the time of manufacture.